Automatic load distributing apparatus for generator and method of controlling same

ABSTRACT

An automatic load distributing apparatus for generators is of simple construction and occupies a small space and can automatically distribute loads evenly on respective engines upon parallel load operation of generators of different capacities and provide labor saving of operation. The automatic load distributing apparatus for generators comprises a plurality of engines for driving a plurality of generators connected in parallel to a common load, a plurality of fuel injection pumps and a plurality of load distributing units for distributing outputs corresponding to the load to the engines. The apparatus comprises a first rotational speed sensor (31a) and a first rack sensor (4a) installed on a first engine (2a), respective rotational speed sensors and respective rack sensors installed on respective engines other than the first engine, first control means (11a) for receiving a signal from the first rack sensor to determine a load factor for the first engine to issue the same to the respective engines, and respective control means for determining respective load factors for the respective engines and comparing them with the signal from the first control means to output commands to respective fuel injection pumps so as to make the respective load factors to be identical to a load factor of the first engine which has become a maximum load factor. Also the first control means prevents overload by sequentially issuing startup commands to respective self-starting motors (13b) when a load factor of the first engine exceeds a predetermined value.

TECHNICAL FIELD

The present invention relates to an automatic load distributingapparatus for generators, and in particular, to an automatic loaddistributing apparatus for operating a plurality of diesel engine drivengenerators connected in parallel.

BACKGROUND ART

When a plurality of diesel engine driven generators are connected forparallel load operation, an automatic load distributing apparatus isprovided to make loads on the respective generators substantially even.FIG. 8 is for explaining general construction of an automatic loaddistributing apparatus which is frequently used for conventionalgenerators driven by diesel engines with Bosch fuel injection pumps.

Upon parallel load operation of such generators, a first diesel enginedriven generator 20a and a second diesel engine driven generator 20b arearranged in parallel. The first diesel engine driven generator 20a isconnected to a bus bar 23 via a wire 21a and a first breaker 22a. Thesecond diesel engine driven generator 20b is also connected to the busbar 23 via a wire 21b and a second breaker 22b.

The first diesel engine driven generator 20a is constructed of a firstengine 24a, a first generator 25a, a first load distributing unit 26a,and a first rotational speed controller 27a. The second diesel enginedriven generator 20b is of the same construction as the first dieselengine driven generator 20a and the description thereof is omitted belowby labeling respective elements with corresponding reference numerals.

The first engine 24a is constructed of a first Bosch fuel injection pump28a, a first governor 29a, a first actuator 30a, and a first rotationalspeed sensor 31a. A control lever 32a, installed on the first governor29a, and a lever 33a, installed on the first actuator 30a, are connectedby a rod 34a. The first actuator 30a and the first rotational speedcontroller 27a are connected by a wire 35a; the first rotational speedsensor 31a and the first rotational speed controller 27a are connectedby a wire 36a.

The first load distributing unit 26a is connected to the firstrotational speed controller 27a via a wire 37a, and to bus bars 38 and40 of parallel line via wires 39a and 41a, respectively. The first loaddistributing unit 26a and the first generator 25a are connected via botha voltage detecting wire 42a and a current detecting wire 43a.

Hereinbelow, the description will be made first of a single loadoperation of the first generator 25a in the first diesel engine drivengenerator 20a, and then to a parallel load operation of the firstgenerator 25a and the second generator 25b in the second diesel enginedriven generator 20b.

First of all, the single load operation of the first generator 25a isdescribed with reference to FIG. 2. FIG. 2 shows the rack position ofthe first fuel injection pump 28a in ordinate and the rotational speedof the first fuel injection pump 28a in abscissa. The rack position inthe ordinate has one to one correspondence to the load factor of theoutput of the first engine 24a. Indicated from an operating point a toan operating point b is the upper limit of the rack position, whichcorresponds to 100% of the load factor. An operating point j indicates arated output/rated rotational speed of the first engine 24a. Indicatedfrom the operating point b to an operating point c is an actual range ofuse, which corresponds to an operating range of the first governor 29a.A rated rotational speed A is determined by the number of electrodes andthe frequency of the generator in the case of an engine for thegenerator, where the engine is operated at constant rotational speed.

Upon no-load operation after completion of engine warm-up, the rackposition is at an operating point c. Then when the first generator 25ais connected to the bus bar 23 by turning the first breaker 22a "ON" anda load, e.g., of 80% of the generator rated output value, is applied tothe first generator 25a from the outside, the first governor 29a acts totransitionally move the rack position from the operating point c to anoperating point d. At the same time, the amount of fuel injection to thefirst engine 24a, and hence its output power, increases. However, therotational speed at the operating point d is decreased by B from therated rotational speed A, and needs to be increased to an operatingpoint e.

The increase in the rotational speed from the operating point d to theoperating point e is controlled by the first rotational speed controller27a. In this case, an engine rotational speed signal from the firstrotational speed sensor 31a is inputted to the first rotational speedcontroller 27a via the wire 36a. Upon receipt of the signal, the firstrotational speed controller 27a sends a signal corresponding to theincreased rate B of the rotational speed to the first actuator 30a viathe wire 35a to move the lever 33a on the first actuator 30a in adirection of "INCREASE" in rotational speed, and hence the control lever32a via the rod 34a. Thus the rotational speed is increased, and thesingle load operation of the first generator 25a is carried out at theoperating point e by an engine output corresponding to a load of 80% ofthe rated output value of the first generator 25a.

Next, a parallel load operation of the first generator 25a and thesecond generator 25b will be is described with reference to FIGS. 3 and4. As an example, the description is made to a case where the firstgenerator 25a is operated while gradually decreasing its load from 80%to 40% and the second generator 25b is operated from an unloadedcondition while gradually increasing its load from 0% to 40%.

The 80% loaded operation of the first generator 25a is indicated at theoperating point e in FIG. 3; the unloaded operation of the secondgenerator 25b is indicated at an operating point g in FIG. 4. From thisoperating condition, the second breaker 22b is turned "ON" to connectthe second generator 25b to the bus bar 23 so as to start parallel loadoperation.

A comparison between the 80% load factor of the first generator 25a andthe 0% load factor of the second generator 25b is made by the first loaddistributing unit 26a and the second load distributing unit 26b. In thiscase, an output signal from the first generator 25a is inputted to thefirst load distributing unit 26a via the voltage detecting wire 42a andthe current detecting wire 43a. At the same time, an output signal fromthe second generator 25b is inputted to the second load distributingunit 26b via the voltage detecting wire 42b and the current detectingwire 43b. Then, an output signal from the second load distributing unit26b is inputted to the first load distributing unit 26a via a wire 41b,the bus bar 40 of parallel line, and the wire 41a. The first loaddistributing unit 26a compares the output signal corresponding to the80% load factor of the first generator 25a with the output signalcorresponding to the 0% load factor of the second generator 25b andprocesses the comparison result to output a signal to the firstrotational speed controller 27a so as to reduce the rotational speed ofthe first engine 24a. The first rotational speed controller 27a performscontrol, using the signal for reducing the rotational speed of the firstengine 24a and a signal from the first rotational speed sensor 31a tosend a signal corresponding to a rotational speed drop rate C to thefirst actuator 30a via the wire 35a. This signal moves the lever 33a onthe first actuator 30a in a direction of "DECREASE" in rotational speed,and hence the control lever 32a via the rod 34a. Thus the engine speedis reduced.

The second generator 25b is also operated in a manner similar to thefirst generator 25a to increase the engine speed.

Through the above operation, the load factor of the first generator 25ais gradually decreased from 80% to 40%, the load factor of the secondgenerator 25b is gradually increased from 0% to 40%, and they arefinally made to be equivalent. In other words, the loaded condition ofthe first generator 25a in FIG. 3 is gradually decreased from its 80%load factor at the operating point e to its 40% load factor at anoperating point f, while the loaded condition of the second generator25b in FIG. 4 is gradually increased from its 0% load factor at theoperating point g to its 40% load factor at an operating point h. Thus,the loads are automatically evenly distributed on the engines for thefirst and second generators 25a and 25b at a load factor of 40%.

Such a conventional technique, however, causes the following problemswith the first and second load distributing units 26a and 26b.

(1) The loads for the first and second generators 25a and 25b aredetected as signals from the generators. Since such outputs are toolarge, the voltage and current signals are necessarily drawn throughrespective transformers. Further, since the wiring is of a three-phasetype, a total of six wires, three for voltage plus three for current, isrequired. This increases the number of assembling steps associated withthe wiring on the outgoing side of the first and second generators 25aand 25b and the side of the first and second load distributing units 26aand 26b, and makes the entire construction complicated in cooperationwith the provision of the transformers required for drawing voltage andcurrent signals.

(2) If the apparatus is designed to obtain loads on the first and secondgenerators 25a and 25b at a high voltage, such as 400 volts, withouttransformers, there is a danger of shock due to mishandling inmaintenance and outfitting operations. Such a case requires skilledtechnical experts to work.

(3) Since the control apparatus for the first and second generators 25aand 25b is divided into a group of the first and second loaddistributing units 26a and 26b and a group of the first and secondrotational speed controllers 27a and 27b, it occupies a large space.Mounting brackets are also required for respective control components,and hence the number of assembling steps is increased.

(4) Assuming that the first generator 25a is a 400-kilowatt generatorand the second generator 25b is a 200-kilowatt generator, voltage andcurrent transformers for 400 kilowatts and 200 kilowatts need to bemounted respectively on the first generator 25a and the second generator25b when both generators are connected for parallel load operation. Inthis case, when the transformer for 400 kilowatts is incorrectly mountedon the second generator 25b like the first generator 25a upon parallelload operation, the respective load factors of the first and secondgenerators remain uneven. If a load of 450 kilowatts is applied from theoutside during the parallel load operation, the first generator 25a isloaded at 225 kilowatts and its load factor is 56.3%, while the secondgenerator 25b is loaded at 225 kilowatts and its load factor is 112.5%.As a result, the second engine 24b for driving the second generator 25bexceeds its rated power and has operational problems.

DISCLOSURE OF THE INVENTION

In consideration of the conventional problems, it is an object of thepresent invention to provide an automatic load distributing apparatusfor generators and a method of controlling the same, in which theapparatus is of simple construction and occupies a small space, requiresno transformers and hence reduces the number of assembling steps withoutany danger of shock, and can automatically distribute loads evenly onthe respective engines upon parallel load operation of generators ofdifferent capacities, and provides labor saving of operation.

According to a first aspect of the present invention, an automatic loaddistributing apparatus for generators comprises a plurality ofgenerators connected in parallel to a common load, a plurality ofengines for driving the respective generators, a plurality of fuelinjection pumps installed on the respective engines, and a plurality ofload distributing units for distributing outputs corresponding to theloads on the engines.

The apparatus comprises a first rotational speed sensor for detectingthe rotational speed of a first engine; a first rack sensor fordetecting the load on the first engine; a second rotational speed sensorfor detecting the rotational speed of a second engine; first controlmeans for receiving signals from the first rotational speed sensor andthe first rack sensor for detecting the load on the first engine, foroutputting a command to a first fuel injection pump so as to maintainthe first engine at a constant rotational speed which can be increasedor decreased according to the load, and for outputting a command to asecond control means to increase the load on the second engine when theload on the first engine exceeds the load on the second engine; and thesecond control means for comparing the load signal from the firstcontrol means with the load on the second engine to output a command toa second fuel injection pump so as to make the load on the second engineto be identical to that on the first engine.

In such construction, loads are automatically distributed evenly on thefirst and second engines. Since the construction is simplified bydetecting the load on the first engine at the first rack sensor and byintegrating a first load distributing unit with a first rotational speedcontroller, the first control means is made compact to reduce the spaceoccupied by the apparatus to one-half of the conventional one. Also,since outgoing connections for load detection can be of simple singlephase wiring of low voltage and low current without the need for atransformer, the number of assembling steps is largely reduced, andbesides, safety is improved without danger of shock due to mishandlingin maintenance and outfitting operations. Furthermore, although theconventional apparatus has caused such a problem that an engine hasoperational problems upon parallel load operation of generators ofdifferent capacities because of uneven load factors, resulting fromincorrect mounting of transformers of an identical capacity, it isimproved by having the first rack sensor detect the load.

According to a second aspect of the present invention, the second engineincludes a second rotational speed sensor and a second rack sensor fordetecting the load on the second engine. In this case, the first controlmeans receives signals from the first rotational speed sensor and thefirst rack sensor for detecting the load on the first engine. Then, thefirst control means outputs a command to the first fuel injection pumpso as to maintain the first engine at a constant rotational speed, andwhen the load on the first engine exceeds the load on the second engine,outputs a command to the second control means to increase the load onthe second engine. As the load on the second engine increases, the loadon the first engine automatically decreases. Then when the loads on thefirst and second engines are made to be identical, the command toincrease the load on the second engine is stopped.

In such construction, the apparatus can distribute loads evenly if theload on the second engine is heavier than that on the first engine aswell as achieve the same improvements as in the first aspect of thepresent invention.

According to a third aspect of the present invention, an automatic loaddistributing apparatus for generators comprises a plurality ofgenerators connected in parallel to a common load, a plurality ofengines for driving the respective generators, a plurality of fuelinjection pumps installed on the respective engines, and a plurality ofload distributing units for distributing outputs corresponding to theloads on the engines.

The apparatus comprises: a first rotational speed sensor, for detectingthe rotational speed of a first engine; a first rack sensor, fordetecting the load on the first engine; respective rotational sensorsfor detecting respective rotational speeds of engines other than thefirst engine; respective rack sensors for detecting the loads on therespective engines; first control means for receiving signals from thefirst rotational speed sensor and the first rack sensor for detectingthe load on the first engine, and for determining a load factor(output/rated output×100) for the first engine to issue the same to therespective engines; and respective control means for determiningrespective load factors for the respective engines and for comparingthem with the signal from the first control means to output commands torespective fuel injection pumps so as to make the respective loadfactors to be identical to the load factor of the first engine which hasbecome a maximum load factor.

In such construction, the apparatus can automatically distribute loadsevenly on the first engine and the other respective engines as well asachieve the same improvements as in the first aspect of the presentinvention.

According to a fourth aspect of the present invention, the first engineand the respective engines other than the first engine further comprisea first self-starting motor and other respective self-starting motors,respectively. Also, the first control means receives the signals fromthe first rotational speed sensor and the first rack sensor fordetecting the load on the first engine, and determines the load factorfor the first engine, to issue startup commands to the respectiveself-starting motors sequentially so as to prevent overload when theload factor for the first engine exceeds a predetermined value.

In such construction, the apparatus can automatically distribute loadsevenly on the first engine and the engines that have received thestartup commands, and can provide savings in labor operations.

According to a fifth aspect of the present invention, a method ofcontrolling an automatic load distributing apparatus for generatorscomprises the step of starting a plurality of engines, for driving aplurality of generators connected in parallel to a common load,sequentially according to the common load to distribute outputscorresponding to the common load to the engines.

The control method comprises the steps of starting the plurality ofengines sequentially according to the common load to determine therespective load factors so as to detect a maximum load factor as aresult of the comparison of the respective load factors, transmittingthe maximum load factor sequentially to engines other than the engine ofwhich the load factor has become the maximum load factor, and increasingthe load factors of the respective engines sequentially in such a manneras to make the load factor of each engine identical to the maximum loadfactor.

Such a control method allows the apparatus to automatically distributeloads evenly on the engines and provide savings in labor operations.

In addition, the automatic load distributing apparatus for generatorsand the control method therefor require only one parallel line bus barfor the signal of the maximum load factor, and this makes the bus barsimple.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the general construction of an automatic loaddistributing apparatus for generators according to a first embodiment ofthe present invention;

FIG. 2 is a diagram for explaining single operations of a firstgenerator of the present invention and that of the prior art;

FIGS. 3 and 4 are diagrams for explaining plural load operations offirst and second generators of the present invention and those of theprior art;

FIG. 5 is a diagram of the general construction of an automatic loaddistributing apparatus for generators according to a second embodimentof the present invention;

FIG. 6 is a flowchart showing a first example of the operation of theautomatic load distributing apparatus for generators according to thesecond embodiment of the present invention;

FIG. 7 is a flowchart showing a second example of operation of theautomatic load distributing apparatus for generators according to thesecond embodiment of the present invention; and

FIG. 8 is a diagram of the general construction of a conventionalautomatic load distributing apparatus for generators.

BEST MODES FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 to 4, the first embodiment of the present inventionwill be described in detail.

FIG. 1 is a diagram of the general construction of an automatic loaddistributing apparatus for generators. Components common to those of theprior art are given the same reference numerals and the descriptionthereof is omitted. Also, components in a first diesel engine drivengenerator 1a are given a suffix a and components in a second dieselengine driven generator 1b are given a suffix b. Hereinbelow, thedescription is made of the first diesel engine driven generator 1a. Thesecond diesel engine driven generator 1b has the same construction andthe description thereof is omitted.

The first and second diesel engine driven generators 1a and 1b arearranged in parallel. The first diesel engine driven generator 1a isconnected to a bus bar 23 via a wire 21a and a first breaker 22a. Thefirst diesel engine driven generator 1a is constructed of a first engine2a, a first generator 25a, and a first controller 3a as a control means.

The first engine 2a is constructed of a first Bosch fuel injection pump28a, a first governor 29a, a first actuator 30a, a first rotationalspeed sensor 31a, and a first rack sensor 4a. A control lever 32a,installed on the first governor 29a, and a lever 33a, installed on thefirst actuator 30a, are connected by a rod 34a. The first actuator 30aand the first rotational speed controller 3a are connected by a wire 6a;the first rack sensor 4a and the first controller 3a are connected by awire 7a.

The first controller 3a and a parallel line bus bar 38 are connected bya wire 8a. The bus bar 38 is always supplied with a signal indicative ofthe maximum load factor of the engines arranged in parallel. The firstactuator 30a can be directly connected to a rack so that the firstgovernor 29a, the control lever 32a, and the rod 34a can be omitted.

Hereinbelow, description will be made first of a single load operationof the first diesel engine driven generator 1a, and then to a parallelload operation of the first diesel engine driven generator 1a and thesecond diesel engine driven generator 1b.

The single load operation of the first diesel engine driven generator 1ais described with reference to FIG. 2. FIG. 2 shows the rack position(mm) of the first fuel injection pump 28a in ordinate and the rotationalspeed (rpm) of the first fuel injection pump 28a in abscissa. The rackposition in the ordinate has one to one correspondence to the loadfactor (%) of engine output. Indicated from an operating point a to anoperating point b is the upper limit of the rack position, whichcorresponds to 100% of the load factor. An operating point j indicates arated output/rated rotational speed of the engine 2a. Indicated from theoperating point b to an operating point c is an actual range of use,which corresponds to an operating range of the first governor 29a. Arated rotational speed A is determined by the number of electrodes andthe frequency of the generator in case of an engine for the generator.For example, if the number of electrodes is 4 and the frequency is 60Hz, the rated rotational speed A is 1800 rpm.

Upon no-load operation after completion of engine warm up, the rackposition is at an operating point c. Then when the first generator 25ais connected to the bus bar 23 by turning the first breaker 22a "ON" anda load, e.g., of 80% of the rated output value, is applied to the firstgenerator 25a from the outside, the first governor 29a acts to shift therack position from the operating point c to an operating point d. At thesame time, the amount of fuel injection to the first engine 2a, andhence its output power, increases. However, the rotational speed at theoperating point d is decreased by B from the rated rotational speed A,and needs to be increased to an operating point e.

The increase in the rotational speed from the operating point d to theoperating point e is controlled by the first controller 3a. In thiscase, an engine rotational speed signal from the first rotational speedsensor 31a is inputted to the first controller 3a via the wire 6a. Uponreceipt of the signal, the first controller 3a inputs a signalcorresponding to the increased rate B of the rotational speed to thefirst actuator 30a via the wire 5a to move the lever 33a on the firstactuator 30a in a direction of "INCREASE" in rotational speed, and hencethe control lever 32a via the rod 34a. The rotational speed is increasedto a predetermined rotational speed, e.g., to a rated rotational speed Aof 1800 rpm.

Thus the single load operation of the first diesel engine drivengenerator 1a is carried out at the operating point e by an engine outputcorresponding to a load of 80% of the rated output value of the firstgenerator 25a.

Next, a parallel load operation of the first and second diesel enginedriven generators 1a and 1b will be described with reference to FIGS. 3and 4.

First of all, the description is made of a first example of operation inwhich the first generator 25a is operated while gradually decreasing itsload from 80% to 40% and the second generator 25b is operated from anunloaded condition while gradually increasing its load from 0% to 40%.

The 80% loaded operation of the first generator 25a is indicated at theoperating point e in FIG. 3; the unloaded operation of the secondgenerator 25b is indicated at an operating point g in FIG. 4. Anoperator starts the second engine 2b when the load on the firstgenerator 25a exceeds 80%, and then turns on the second breaker 22b whena temperature rise in the second engine 2b above a predetermined valueis detected. The load on the first engine 1a is inputted to controlmeans, or the second controller 3b, via respective wires 8a and 8b. Thesecond controller 3b compares the load on the first engine 2a inputtedthereto with the load on the second engine 2b, calculates the amount offuel injection required for increasing the load on the second engine 2b,and outputs a command so as to inject a predetermined amount of fuelinto the second fuel injection pump 28b. As the load on the secondengine 2b increases due to the increase in the amount of fuel injection,the load on the first engine automatically decreases. When the loads onthe first and second engines 2a and 2b have become identical, theincreasing of the load on the second engine 2b is stopped, thusautomatically distributing loads evenly on the first and second engines2a and 2b.

Next, the description is made of a second example of parallel loadoperation according to the embodiment.

In this case, a comparison between the 80% load factor of the firstgenerator 25a and the 0% load factor of the second generator 25b is madevia the parallel line bus bar 38. The first rack sensor 4a, installed onthe first fuel injection pump 28a, detects an output of the first engine2a. The detected signal is inputted to the first controller 3a via thewire 7a, and a load factor is calculated therefrom. At the same time,the second rack sensor 4b, installed on the second fuel injection pump28b, detects an output of the second engine 2b. The detected signal isinputted to the second controller 3b via the wire 7b, and a load factoris calculated therefrom. Then, only the larger one of the load factorscalculated at the first and second controllers 3a and 3b is supplied tothe parallel line bus bar.

In other words, only the larger one of two signals is supplied to theparallel line bus bar 38: one indicating a rack position correspondingto the 80% load factor of the first generator 25a, the other for a rackposition corresponding to the 0% load factor of the second generator25b. Since the load factor of the first generator 25a is identical tothe load factor of the parallel line bus bar 38, the first controller 3adoes not issue a command that its load factor be changed. On the otherhand, since the load factor of the second generator 25b is smaller thanthe load factor of the parallel line bus bar 38, the second controller3b issues a command to the second actuator 30b so as to increase itsload factor. If the load factor of the second generator 25b is 10%,since the total load factor is 80%, the load factor of the firstgenerator 25a drops to 70%, and the signal flowing through the parallelline bus bar 38 also becomes 70%. The 10% load factor of the secondgenerator 25b, however, remains lower than the 70% load factor of theparallel line bus bar, and the command that the load factor be changedis continuously issued from the second controller 3b.

Such operation achieves the automation of a gradual transition of theload factor, so that the load factor of the first generator 25a becomes80, 70, 60, 50 and 40%, the load factor of the second generator 25bbecomes 0, 10, 20, 30 and 40%, and finally the load distribution is madeeven. In other words, the loaded condition of the first generator 25a inFIG. 3 is decreased from the 80% load factor at the operating point e tothe 40% load factor at the operating point f, while the loaded conditionof the second generator 25b in FIG. 4 is increased from the 0% loadfactor at the operating point g to the 40% load factor at the operatingpoint h. Thus the loaded conditions of both generators are madeequivalent at the 40% load factor. In this embodiment, the descriptionwas made to the case where the first generator 25a is started at a highload factor of 80%. Conversely, the second generator 25b can be startedat the high load factor of 80%.

Referring next to FIGS. 5 to 7, the second embodiment of the presentinvention will be described.

In this embodiment, a description is made of a first example of acontrol operation in which the load factor of the first engine 2a iscompared with the load factors of respective engines other than thefirst engine 2a, and the load factors of the respective engines are madeto be identical to the load factor of the first engine 2a. Next, adescription is made of a second example of automatic control operationin which respective engines for driving a plurality of generators arestarted sequentially according to a load, and the load factor issequentially increased for each engine, except the one that has amaximum load factor, in such a manner as to make each load factoridentical to the maximum load factor.

FIG. 5 is a diagram of the general construction of an automatic loaddistributing apparatus for generators. Components common to those of thefirst embodiment are given the same reference numerals and thedescription thereof is omitted. Hereinbelow, the description is made ofthe first diesel engine driven generator 1a. The second diesel enginedriven generator 1b has the same construction and the descriptionthereof is omitted.

In FIG. 5, constructive differences between this embodiment and thefirst embodiment are present in a first controller 11a and a firstself-starting motor 13a. The first controller 11a is connected to a busbar 12 via a wire 14a, and to the first self-starting motor 13a via awire 15a.

First of all, a description is made to a first example of operationaccording to the embodiment with reference to the flowchart of FIG. 6.

FIG. 6 is a flowchart of a control operation in which the load factor ofthe first engine 2a is compared with the load factors of respectiveengines other than the first engine 2a and the load factors of therespective engines are made to be identical to the load factor of thefirst engine 2a.

In step 1, the rotational speed and the rack position of the firstengine 2a are detected. The rotational speed signal from the firstrotational speed sensor 31a is inputted to the first controller 11a viathe wire 6a. The rack position signal from the first rack sensor 4a isinputted to the first controller 22a via the wire 7a.

In step 2, a load factor is determined for the first engine 2a. Thefirst controller 11a operates the input signals to determine the loadfactor.

In step 3, the load factor of the first engine 2a is transmitted to therespective engines other than the first engine 2a. For example, the loadfactor is transmitted from the first controller 11a to a secondcontroller lib via the wire 14a, the parallel line bus bar 12 and thewire 14b.

In step 4, the rotational speeds and the rack positions of respectiveengines other than the first engine 2a are detected.

For example, the rotational speed of the second engine 2b is detected bythe second rotational speed sensor 31b and inputted to the secondcontroller 11b via the wire 6b. The rack position is detected by thesecond rack sensor 4b and inputted to the second controller 11b via thewire 7b.

In step 5, the load factors are determined for the respective enginesother than the first engine 2a. For example, the second controller 11boperates the input signals to determine the load factor for the secondengine 2b. The load factor is transmitted to the parallel line bus bar12.

In step 6, the load factor of the first engine 2a, transmitted to theparallel line bus bar 12, is compared with the load factors of the otherrespective engines. For example, the second controller 11b compares theload factor transmitted from the first engine 2a with the load factor ofthe second engine 2b.

In step 7, the amount of fuel injection to each respective engine iscontrolled in such a manner as to make the load factors of therespective engines identical to the load factor of the first engine 2a.For example, the amount of fuel injection to the second engine 2b iscontrolled in such as manner as to make the load factor of the secondengine 2b identical to the load factor of the first engine 2a which hasbecome a maximum load factor. To do this, a signal is sent from thesecond controller 11b to the actuator 30b via the wire 5b to actuate thesecond governor 29b via the lever 33b, the rod 34 and the control lever32b.

As described above, the load factor of the first engine 2a and the loadfactors of the other respective engines are compared, and the amount offuel injection to the other respective engines is controlled in such amanner as to make the load factors of the respective engines identicalto the load factor of the first engine 2a. This makes it possible toautomatically distribute loads evenly on the first engine 2a and theother respective engines.

Next, a description is made of a second example of operation accordingto the embodiment with reference to the flowchart of FIG. 7.

FIG. 7 is a flowchart of automatic control operation in which respectiveengines for driving a plurality of generators are started sequentiallyaccording to the load, and the load factors of the engines, except onethat has a maximum load, are increased sequentially so as to make theload factor of each engine identical to the maximum load factor. Here, adetailed description of steps common to those in the first example isomitted.

In step 11, the rotational speed and the rack position of the firstengine 2a are detected.

In step 12, a load factor is determined for the first engine 2a by thefirst controller 11a.

In step 13, it is determined whether or not the load factor of the firstengine 2a exceeds a predetermined value. The operation then advances tostep 16 if it exceeds the predetermined value, and to step 14 if not.

In step 14, it is determined whether or not respective engines otherthan the first engine 2a are started. The operation returns to step 11if not started, and advances to step 15 if started.

In step 15, the rearmost engine, other than the first engine 2a, isstopped, and then the operation returns to step 11.

In step 16, startup commands are outputted to self-starting motors ofthe engines other than the first engine 2a. For example, the secondcontroller 11b outputs a startup command to the second self-startingmotor 13b to start the second engine 2b.

In step 17, the rotational speed and the rack position of the engineother than the first engine 2a are detected.

In step 18, a load factor is determined for the engine other than thefirst engine 2a.

In step 19, it is determined whether or not the load factor of the firstengine 2a is equal to that of the engine other than the first engine 2a.The operation then advances to step 20 if not equal, and returns to step11 if equal.

In step 20, the amount of fuel injection to the engine other than thefirst engine 2a is controlled.

In step 21, the rotational speed and the rack position of the firstengine 2a are detected.

In step 22, a load factor is determined for the first engine 2a totransmit the value to the bus bar 12 of parallel line.

In step 23, the load factor of the engine other than the first engine 2ais compared with that of the first engine, and the amount of fuelinjection to the engine is controlled in such a manner as to make theload factor of the engine other than the first engine 2a identical tothe load factor of the parallel line bus bar 12.

Then, the operation returns to step 17, and steps 17 through 23 arerepeated until the load factor of the engine other than the first engine2a becomes equal to that of the first engine 2a.

When both load factors become equal, the operation returns from step 19to step 11. Then, determination is made as to whether or not the loadfactor of the first engine 2a exceeds the predetermined value. If theload factor still exceeds the predetermined value, a further subsequentengine (e.g., a third engine, not shown) is started. If the load valueis below the predetermined value, the engine (e.g., the second engine2b) is stopped.

As described above, the load factor of the first engine 2a is comparedwith the load factor of the subsequent engine to control the amount offuel injection to the engine other than the first engine 2a. If the loadfactor of the first engine 2a has still exceeded the predeterminedvalue, a further subsequent engine is started. Thus loads areautomatically distributed evenly on the first engine 2a and the engineor engines that have received the startup commands.

Although the embodiment was described using the first engine 2a as thebase unit, any other engine such as the second engine 2b can be used asthe base unit. In this case, the load factor of the second engine 2b iscompared with a load factor of an engine other than the second engine 2bto control the amount of fuel injection to the engine compared.

According to the present invention, the automatic load distributingapparatus for parallel load operation of a plurality of generatorsconnected in parallel is such that loads on the generators are detectedat rack sensors of respective engines, and the control means is madecompact by integrating a first load distributing unit with a firstrotational speed controller, and the construction is simplified toreduce the space occupied by the apparatus to one-half of theconventional one. Also, since outgoing connection for load detection canbe of simple single-phase wiring of low voltage and low current withoutthe need for a transformer, the number of assembling steps is largelyreduced, and the danger of shock due to mishandling in maintenance andoutfitting operations is avoided. Further, loads can be automaticallydistributed evenly on respective engines upon parallel load operation ofgenerators of different capacities.

In addition, the control method allows the apparatus to command that theengines are started sequentially while confirming the maximum engineload factor and increase the load factor for each engine in such amanner as to make that load factor to be identical to the maximum loadfactor. This makes it possible to provide labor saving of operation. Theparallel line bus bar can also be simplified since it is required forthe maximum load factor signal alone.

Industrial Applicability

The present invention is applicable to an automatic load distributingapparatus and a control method therefor, in which the apparatus is ofsimple construction and occupies a small space, and can automaticallydistribute loads evenly on respective engines upon parallel loadoperation of generators of different capacities and provide labor savingof operation.

I claim:
 1. An automatic load distributing apparatus comprising:aplurality of generators connected in parallel to a common load; aplurality of engines, each of said engines being adapted to drive arespective one of said plurality of generators, said plurality ofengines including a first engine and a second engine; a plurality offuel injection pumps, each of said fuel injection pumps being installedon a respective one of said plurality of engines; a first rotationalspeed sensor for detecting a rotational speed of said first engine; afirst rack sensor for detecting a load on said first engine; a secondrotational speed sensor for detecting a rotational speed of said secondengine; first control means; and second control means; said firstcontrol means being adapted for receiving signals from said firstrotational speed sensor and said first rack sensor, for outputting acommand to the fuel injection pump for said first engine so as tomaintain said first engine at a constant rotational speed which can beincreased or decreased according to the load on said first engine, andfor outputting a command to said second control means to increase a loadon the second engine when the load on said first engine exceeds the loadon said second engine; and said second control means being adapted forcomparing a load signal from said first control means with the load onsaid second engine and outputting a command to the fuel injection pumpon said second engine so as to make the load on said second engine to beidentical to the load on said first engine.
 2. An automatic loaddistributing apparatus in accordance with claim 1, further comprising asecond rack sensor for detecting a load on said second engine;andwherein said first control means receives signals from said firstrotational speed sensor and said first rack sensor, outputs a command tothe fuel injection pump for said first engine so as to maintain saidfirst engine at a constant rotational speed which can be increased ordecreased according to the load on said first engine, outputs a commandto said second control means to increase the load on said second enginewhen the load on said first engine exceeds the load on said secondengine, and stops increasing the load on said second engine when theloads on said first and second engines have become identical after theoutput of said first engine has automatically decreased accompanying theincrease in the load on said second engine.
 3. An automatic loaddistributing apparatus comprising:a plurality of generators connected inparallel to a common load; a plurality of engines, each of said enginesbeing adapted to drive a respective one of said plurality of generators,said plurality of engines including a first engine; a plurality of fuelinjection pumps, each of said fuel injection pumps being installed on arespective one of said plurality of engines; a first rotational speedsensor for detecting a rotational speed of said first engine; a firstrack sensor for detecting a load on the first engine; each individualone of said plurality of engines other than said first engine having arotational speed sensor associated therewith for determining arotational speed of the respective one of the engines other than thefirst engine; each individual one of said plurality of engines otherthan said first engine having a rack sensor associated therewith fordetermining a load on the respective one of the engines other than thefirst engine; first control means for receiving signals from said firstrotational speed sensor and said first rack sensor, and for determininga load factor (output/rated output×100) for said first engine to issuethe same to the respective engines other than the first engine; and eachindividual one of said plurality of engines other than said first enginehaving a respective control means for determining a load factor for therespective one of the engines other than the first,engine, and forcomparing the load for the respective one of the engines other than thefirst engine with an output of said first control means to output acommand to the fuel injection pump for the respective one of the enginesother than the first engine so as to make the respective load factors tobe identical to the load factor of said first engine which has become amaximum load factor.
 4. An automatic load distributing apparatus inaccordance with claim 3, wherein said first engine comprises a firstself-starting motor and each individual one of the engines other thansaid first engine comprises a respective self-starting motor; andwhereinsaid first control means receives signals from said first rotationalspeed sensor and said first rack sensor, and determines the load factorfor said first engine to sequentially issue startup commands to therespective self-starting motors so as to prevent overload when the loadfactor for said first engine exceeds a predetermined value.
 5. A methodof controlling an automatic load distributing apparatus for generators,said method comprising the steps of:starting at least one of a pluralityof engines, each individual one of said plurality of engines being fordriving a respective one of a plurality of generators which areconnected in parallel to a common load; determining a load factor foreach individual one of said plurality of engines so as to detect amaximum load factor as a result of a comparison of the respective loadfactors; transmitting the maximum load factor sequentially to enginesother than the engine of which the load factor has become the maximumload factor; and increasing the load factors of the respective engines,other than engines of which the load factor has become the maximum loadfactor, sequentially in such a manner as to sequentially make the loadfactor of each engine to be identical to the maximum load factor.